Heavy oil upgrading has attracted worldwide attention because of decreasing conventional sweet crude oil reserves. Heavy crude oil, however, can be converted into usable light oil, and is available in a significant number of unspent reservoirs.
As is understood in the art, coking and hydrocracking are two primary upgrading approaches in the petroleum industry to convert heavy crude oil into light crude oil. It is also known that coking produces large amounts of unmarketable coke, and hydrocracking, often operated in the presence of a catalyst, suffers from operational problems related to catalyst deactivation.
As is known from the prior art, one approach to limiting the effect of catalyst deactivation is to perform the reaction in slurry hydrocracking reactors using unsupported catalysts dispersed in the heavy oil. The degree of the catalyst dispersion is quite important in a slurry process, as it strongly affects the catalyst activity. A well-dispersed catalyst favors the rapid uptake of hydrogen, which prevents free radical condensation among heavy oil molecules that would lead to coke formation.
It is generally agreed that molybdenum-based catalysts provide the best performance in the aforesaid hydrocracking process. Dispersed MoS2 catalysts are usually based on oil-soluble organometallics, such as molybdenum naphthenate, molybdenum dithiocarboxylate and molybdenum dithiophosphate, which are used as precursors. The active form of the so-called catalyst is generated in situ by thermally decomposing the precursor and reacting with sulfur. The sources of sulfur include sulfur originally present in the feedstock, or externally added, suitable sulfur-containing compounds, such as H2S and elemental sulfur. The produced MoS2 through the aforementioned procedure could be in the form of micrometer-sized or nanometer-sized particles. However, in situ production of MoS2 is not complete in that most of the prepared catalyst particles are microparticles.
It should be understood that commercializing the slurry bed reactor for heavy crude oil upgrading is too difficult, which is partly due to the high cost of the MoS2 catalyst, despite the use of low catalyst concentrations. To tackle this problem, one approach is to further reducing the required amount of catalyst concentration (<200 ppm) for the process, while maintaining the overall hydrocracking performance as the same. In addition, the recycling of the MoS2 catalyst is an important issue in catalyst development for an economic slurry hydrocracking process.
There is, therefore, a present need for an improved catalytic, heavy-crude-oil hydrocracking process, as well as a significant reduction of the requisite catalyst concentration required in such processes.
It is, therefore, an object of the present invention to provide a new and improved nanocatalyst for such heavy crude oil upgrading processes. The new catalyst makes it possible to carry out the hydrocracking process with a much lower amount of catalyst than required in prior art processes, and consequently minimizing or eliminating the requirement in the prior art for catalyst recovery.
It is also an object of this invention to lower the operating temperature of the heavy crude oil hydrocracking process.
Furthermore, it is an object of the present invention to increase the efficiency of the hydrocracking process, despite the lower requisite catalyst concentrations.
These objects are met in various embodiments of the present invention where heavy crude oil upgrading nanocatalysts and methods to synthesize the same are described. As a result of this advancement in the technology, hydrocracking processes can be operated with lower amounts of catalyst, thereby saving costs and making the process viable over the prior art techniques for catalyst recovery. Accordingly, the improved, nanocatalysts and the methods for their production, as set forth in the present invention, offer significant advantages over the known prior art.